The work proposed deals with embryonic development and differentiation in the common snapping turtle, Chelydra serpentina. Current objectives are as follows: (1) Production of intersexes and a study of their causes and morphology. (2) Incidences of sex in eggs hatched in outdoor nests and relation of nest temperatures to sex-ratios. (3) Effect of diurnalchanges in incubation temperatures between male and female producing temperatures. In addition, extension of the study to work with eggs of marine turtles, starting with the loggerhead turtle, Caretta caretta.